Cabal is unhelpful when updating `.cabal` version

```
$ cabal check
Warning: libarchive-clib.cabal:6:33:
unexpected Unknown SPDX license identifier: 'OtherLicense' SPDX license list
contains plenty of licenses. See https://spdx.org/licenses/. Also they can be
combined into complex expressions with AND and OR.
Errors encountered when parsing cabal file libarchive-clib.cabal:

libarchive-clib.cabal:6:33: error:
unexpected Unknown SPDX license identifier: 'OtherLicense' SPDX license list contains plenty of licenses. See https://spdx.org/licenses/. Also they can be combined into complex expressions with AND and OR.

5 | version: 3.8.8
6 | license: OtherLicense
| ^
Error: [Cabal-7035]
parse error
```

Cabal should tell me what the new identifier for `OtherLicense` is, instead of bothering me with SPDX licenses and being secretive about what to do.

Start by reproducing the example with `cabal check` and trace where the unknown `OtherLicense` identifier is turned into the current diagnostic. The work is done when the error identifies the replacement identifier or otherwise explains what to use instead, with coverage for this case.

Written by the indexing model from the issue text.